The Facebook-owned social network said it had “fully resolved” the issue which it said had earlier caused the app to be down “for some users”.
Users had earlier taken to other social media sites, including Twitter, to confirm issues with the app, with the hashtag #instagramdown quickly trending.
According to web service monitoring site Down Detector, users across Europe – including the UK – as well as the United States and parts of South America and Asia were affected by the outage.
“We know this is frustrating, and our team is working quickly to fix it,” Instagram’s initial statement said.
Despite confirming the problem had been resolved, the company has not commented on the cause of the issue or how many people were affected.
Instagram, which Facebook bought for one billion dollars in 2012, has more than a billion active users.